The invention relates to a device for detecting the speed or position of a rotor in a continuously excited electric motor.
A device for detecting rotor speed or rotor position in a continuously excited electric motor by means of a Hall sensor induced by magnetic field pulsation, which is proportional to the rotor speed is known from the French publication FR-A-2 693 054 and the corresponding German publication DE-A1-42 21 424. The Hall sensor in these cases is arranged on the outer circumference of the stator, which surrounds the rotor, in the vicinity of one of the stator-side permanent magnets, which are provided for operationally exciting the electric motor.
The European reference EP-A-0 359 854 discloses a speed measuring device for a rotor-wound electric motor, in which an insulating end plate arranged at the end face of the rotor is constructed to rotate with the rotor and influence an assigned stator-side sensor either magnetically or optically and thereby produce an output which is proportional to the speed of the rotor.